The present invention relates to an assembly for automatically purifying a polluted fluid, and to a method of implementing said assembly.
The invention relates more particularly to treating oils and gas oils for internal combustion engines.
Patent FR 2 725 917 describes a fluid treatment assembly comprising a main separator provided with a backwashing device fed with a fraction of the purified fluid, and a secondary separator fed via the outlet duct of said backwashing device with said fraction as charged with impurities.
Unfortunately, the secondary separator is made up of only one centrifuge whose treatment capacity is constant. The capacity is set once and for all by design to accommodate the mean flow rate of the fraction of fluid that is charged with impurities to be treated and that is delivered from the outlet duct of the backwashing device.
That flow rate is itself dependent on the total flow rate of polluted fluid coming from the motor.
Unfortunately, for a given engine, the polluted fluid flow rate can vary to a considerable extent, in particular as a function of the load on the engine, and it can exceed the predicted values.
Under such conditions, it is sometimes not possible to treat all of the flow rate of charged fluid resulting from backwashing the main separator.
A non-negligible fraction of highly-polluted fluid then returns to the tank, which can ultimately cause the fluid circuits of the engine to become clogged, giving rise to mechanical or hydraulic breakdowns.
In addition, the centrifuge can separate out only those impurities which are of a determined density that corresponds in general to precise values for the pressure and rotation speed parameters.
Thus, impurities that are of density different from the reference value are not always separated out.
When the spectrum of the impurities becomes relatively wide, the effectiveness of the secondary separator is thus significantly reduced.
That also results in problems of clogging and of risks of premature wear or breakdowns.
An object of the present invention is to solve the above-mentioned technical problems satisfactorily by adjusting the capacity and the selectivity of the secondary separator to match respectively the flow rates to be treated and the density of the impurities.
This object is achieved by means of an assembly for automatically and continuously purifying a polluted fluid, said assembly comprising a main separator provided with a backwashing device fed with a fraction of the purified fluid, and a secondary separator fed via the outlet duct of said backwashing device with said fraction of fluid as charged with impurities;
said assembly being characterized in that said secondary separator comprises a combination of a centrifuge device and of a filter device whose capacity and selectivity can be varied as a function firstly of the flow rate of said fraction of fluid charged with impurities and secondly of the range of densities of said impurities.
According to an advantageous characteristic, said centrifuge device and said filter device are mounted in parallel on the outlet duct of the backwashing device.
In a first embodiment, said centrifuge device comprises at least one centrifuge and preferably two centrifuges in parallel.
In another embodiment, said filter device comprises at least one filter having filtering walls.
According to another characteristic, the outlet duct of the backwashing device is equipped with a multi-port valve making it possible to isolate at least a portion of the centrifuge device and/or of the filter device.
According to yet another characteristic, said secondary separator and said main separator are enclosed inside a common casing.
In a particular embodiment, the outlet duct of the backwashing device has a rectilinear upstream segment which extends coaxially with the longitudinal axis of the main separator and which splits into two downstream branches that diverge or that extend in opposite directions, each of which feeds a respective portion of the secondary separator.
In a variant embodiment, said secondary separator is disposed transversely to the main separator.
In another variant, said secondary separator and said main separator are disposed side-by-side.
The invention also provides a method of automatically and continuously purifying a polluted fluid, said method comprising retaining impurities in a main separator, backwashing the main separator with a fraction of purified fluid, and entraining said fraction as charged with impurities to a secondary separator where the impurities are extracted from said fraction;
said method being characterized in that, in the secondary separator, said fraction charged with impurities is centrifuged and filtered, and in that the capacity and the selectivity of the secondary separator are adjusted as a function respectively of the flow rate of said fraction charged with impurities, and of the density of said impurities.
According to a characteristic of the method, the capacity and the selectivity of the secondary separator are adjusted automatically by feeding all or a portion of it or by isolating all or a portion of it.
The purification assembly and the method of the invention make it possible to obtain highly-effective separation of the impurities with a wide density spectrum and regardless of the flow rate of the polluted fluid to be treated.
Regulating and adapting operation of the secondary separator to match the characteristics of the polluted fluid to be purified is performed automatically. By combining a filter with a centrifuge inside the secondary separator, it is possible to guarantee a high level of fluid clarification.
In addition, all of the components of the purification assembly are enclosed in a common casing in an ergonomic layout offering maximum compactness.